Slide projection overlapping apparatus

ABSTRACT

A slide projection overlapping apparatus comprising at least two slide projectors associated with a switching device capable, upon advent of a projection terminating signal thereto, of shifting the connections between the slide projectors enabling discontinuity to be avoided in the projections of successive views at transition from the projected slide projector to the next one. The switching device is provided with delay means for delaying by predetermined time intervals the projection terminating signal to be given to at least one of the said slide projectors with the lamp circuits which are intended to be opened and closed in predetermined sequence.

United States Patent [1 1 Uchidoi et 211.

ill] 3,922,081

1 1 Nov. 25, 1975 l l SLIDE PROJECTION OVERLAPPING APPARATUS [75] Inventors: Masanori Uchidoi. Yokohama;

Tateo Yamada, Tokyo, both of Japan [73] Assignee: Canon Kabushiki Kaisha, Tokyo.

Japan Filed: Nov. 7, 1973 [21] Appli Noll-113.661

[30] Foreign Application Priority Data l\lo\. 11, 197?. Japan 47429977 [52] US. Cl. 353/86 [51] 1nt.C1.- G03B 23/16 [58] Field of Search 353/83, 86, 90. 93, 94', 352/91 R, 91 C, 91 T [56] References Cited UNITED STATES PATENTS 3.181.155 11/1966 Clear 353/86 Broom 1 1 1 1 i a 1 v 353/94 Nm l v v 1 1 i i 4 l 353/86 Primary E.\'aminerRichard E. Aegerter Ass/stall! E.\mniner-A. Jason Mirahito Attorney, Agent. or Fil'Hl-TOTBIL McGeacly and Stanger [57] ABSTRACT A slide projection overlapping apparatus comprising at least two slide projectors associated with a switching device capable. upon advent of a projection terminating signal thereto. of shifting the connections be tween the slide projectors enabling discontinuity to be avoided in the projections of successive views at transition from the projected slide projector to the next one. The switching device is provided with dela means for delaying by predetermined time intervals the projection terminating signal to be given to at least one of the said slide projectors with the lamp circuits which are intended to be opened and closed in predetermined sequence 5 Claims, 5 Drawing Figures lc c /PT2 L J 3 Trr if 08 q Nov. 25, 1975 Sheet 1 of2 3,922,081

U.S. Patent US. Patent Nov. 25, 1975 Sheet 2 of2 3,922,081

FIG.2A

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cunem fol T2P/%fo3 MHmfw fofl flm foo hpvfoz TBP \WSP W Time F l G. 28 Eleciric current To: To T40 10 T05 T60 for Too W13 103% T5 \{Wfos in Time luminance F I 3 To fr '-'-(SEC.) Time SLIDE PROJECTION OVERLAPPING APPARATUS BACKGROUND OF THE INVENTION This invention relates to projection overlapping ap paratus for use in multiple slide projector arrangements enabling discontinuity to be avoided in the projections of successive views in the transition from one slide projector to the other slide projector.

Slide projectors having automatic slide changing devices incorporated therein are known which in the same slide projector enable discontinuity to be avoided in the projection of successive views inasmuch as several tens of slide films are mounted therein. Owing to the lack of necessity of manually replacing the projected slide with a fresh one, such slide projectors have an advantage of enabling one to display images in a continuous succession of projections, while, in most cases, unavoidably restricting the number of slides replaceable in a continuous succession during one operating cycle to as few as 50.

With a slide projector of the type described above, however, a long-run lecture which is intended to be illustrated with more than 50 slides has to be interrupted at transition between the successive operating cycles. In order to reduce the time interval of such a lecture blank which arises when only one slide projector is employed, a plurality of slide projectors have hitherto been employed along with a switching device therefore which is operated to select the slide projector to be lighted in a predetermined order set therein. However, conventional switching devices of the type described above have only the function of shifting the connections between the slide projector merely in succession but without predetermined sequence. Therefore, when BREIF DESCRIPTION OF THE DRAWINGS FIG. I shows an electrical circuit diagram of an embodiment of the projection overlapping apparatus in accordance with the invention adapted for a double slide projector arrangement.

FIGS. 2A and 2B show the typical current waveforms occurring in the lamp circuits of FIG. 1 to illustrate the operation of the slide projection overlapping apparatus of the invention.

FIG. 3 is a graph illustrating variations of illuminance at the projections from the two slide projectors with the projection overlapping apparatus in accordance with a series of slides which are composed so as to display a continuous motion with time (such as actions of mov ing sportsmen) in a continuous succession of operating cycles are projected, the exhibition results in intermittance in the transition from one slide change-operating cycle to the other.

In order to remove the drawback, one solution has been proposed for an overlapping device for projecting two successive views one over the other in the transition from one side projector to the other. With an overlapping device of the conventional type, the first view projected from one slide projector disappears considerably before the second view projected from the other slide projector fades in with a sufficient illuminance, thereupon the two successive views do not completely overlap due to the uncontrolled lighting rates of the lamps of the both projectors, although the lamp circuits are opened and closed simultaneously in synchronism with a slide projector connection shifting signal.

SUMMARY OF THE INVENTION The present invention has for a general object to overcome the drawbacks of conventional switching devices of the type described above, and, therefore, it is an object of the invention to provide a projection overlapping apparatus for use in a multiple slide projector arrangement enabling discontinuity to be avoided in the projections of successive images in the transition from one slide projector to the other slide projector, and, when so required, making it possible to obtain a fading mix effect by projecting gradually two successive views one over the other, the first fading out while the second appearing to fade in and finally replacing it.

the invention during the respective predetermined time intervals having a common portions and distinct portions at transition from one slide projector to the other projector.

FIG. 4 is a top view of a double slide projector arrangement with the projection overlapping apparatus in accordance with the invention therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, there is shown an electrical circuit of a practical embodiment of the projection overlapping apparatus in accordance with the present invention adapted for a double slide projector arrangement. For the purposes of illustration only, the number of lamp circuits is limited to only two. The electrical circuit comprises a transistor Tr which, upon closure of the 15V power source circuit, is made conducting to energize a relay RL,, a transistor Tr which is normally held conductive by the biasing provided by a transistor Tr and which constitutes a part of a flip-flop circuit including another transistor Tr,, a condenser C connected to the base electrode of the transistor Tr a condenser C connected between a remote control switch SW and the flip-flop circuit, a full-wave rectifier circuit REC,, a Zener diode ZD for slicing the pulsating current output of said rectifier circuit REC another Zener diode ZD, for controlling the voltage of the charge stored on the condensers C and C 1 to a predetermined level, diodes D., D D and D for supplying one-directional currents to said two Zener diodes ZD and ZD a control condenser C, of a Darlington connection amplifier (Tr Tr a control condenser C of another Darlington connection amplifier Tr Tr-,, a condenser C connected between the anode and cathod of a programmable uni-junction transistor PUJ, through a primary winding of a pulse transformer PT,, a condenser C connected between the anode and cathode of another programmable uni-junction transistor PUJ through a primary winding of a pulse transformer PT,, and a variable resistor R, for controlling the voltage at the gate of transistor PUJ The lamp circuits of slide projectors I and 2 comprise respectively diodes D and D triacs Tr; and Tr, for controlling the currents flowing through lamps LT, and LT,. circuit portions each consisting of a resistor and a condenser R, and C and R. C for protecting the triacs Tr, and Tr,,, and noise filters of an inductance and a capacitor L, and C,,. and L, and C,. A group of transistors Tr Tr,,, Tr,, and Tr is provided for energizing or deenergizing a slide change plunger of one slide projector, and a group of transistors Tr Tr, Tr and Tr for energizing and deenergizing a slide change plunger of the other slide projector. There are further provided condensers C,,,, C,,, diodes D-,, D, and resistors R,,, R,,,, R,, and R,,.

In a particular embodiment of the switching circuit parameters, the intensities of current flowing through the lamp circuits of the two slide projectors are varied as shown in FIGS. 2A and 28, wherein the ordinates represent current outputs and the abscissae are in time. In order to produce an overlapping effect at the projections of successive two views at transition from one slide projector to the other slide projectors, the two slide projectors may be arranged as illustrated in FIG. 4 wherein a projection overlapping apparatus 1 is connected to slide projectors 2 and 4 positioned in front of a screen 4. For the convenience of explanation, the slide projector arrangement is illustrated as consisting of only two slide projectors as in FIG. 1. However, it is to be noted that the objects of the present invention can be likewise realized in arrangements comprising more than two slide projectors by accommodating for a connection-shifting device such as a ring counter coupled to the projection overlapping apparatus.

Consideration will next be given to the operation of the projection overlapping apparatus. In FIG. 1, as soon as the V power circuit is activated by closing its power source switch not shown and then the power supply source E, is connected to rectifier REC, by means of its power source switch not shown, the transistor Tr, is made conducting to cause a base current to flow in transistor Tr,, thereupon transistor Tr, is driven to conduct, so that the transistor Tr is off" until the voltage across condenser C, reaches a predetermined level, at which level normally no-conducting transistor Tr, is forward biased into conduction. The conductive condition of transistor Tr does not drive transistor Tr, to non-conduct, so that the transistor Tr, is held in conducting state. So long as transistor Tr, is on", the relay RL, is energized to set to the position, b, a circuit transfer switch including, in the present instance, two transfer switch elements SW, and SW, that are commonly interconnected mechanically for conjoint operation from one position to the other position, thereby the lamp LT, of the slide projector l is lighted, while the lamp LT, of the slide projector 2 is not lighted. (The process from the energization of the relay RL, to the lighting of the lamp 1 will be described later).

When a remote control switch SW, is closed to instantaneously generate a slide projector connection shifting signal, a negative pulse is given through condenser C to transistors Tr, and Tr,, so that the conducting transistor Tr, is cut off, while normally notconducting transistor Tr, is switched on. When transistor Tr, is forward biased to conduction, the base current of the transistor Tr, is cut off, and the transistor Tr, is of so that the energization of the relay RL, is terminated, thereupon the transfer switch means SW,, SW, is operated from the position, a, to the position, b. When the pole of the transfer switch element SW, is brought into contact with the throw, b, the full-wave rectifier circuit REC, begins to charge condenser C through diode D,, the contact, b, of the transfer switch clement SW, and the resistor R As the quantity of charge stored on condenser C increases with increase in the base potential of transistor Tr transistors Tr and Tr are made conducting to charge condenser C, from rectifier REC, through resistor R Further sup' plied to condenser C is a quantity of charge through resistor R,,. When the anode potential of transistor PUJ, reaches a predetermined level, transistor PUJ, is made conducting.

After elapse of a certain time period from the initiation of charging of condenser C transistor PUJ, is switched on to instantaneously induce a pulse in the secondary winding of pulse transformer PT,, the pulse triggering the triac Tr through the diode D to make triac Tr, conducting. As a result, at time u the lighting of the lamp LT, of slide projector 2 is initiated, being delayed by a time interval 1, t from the instant t at which the transfer switch element SW, is operated. At time 1 however, the potential of power source E, is reversed to cut off triac Tr thereafter no current flows through lamp LT,. In the next reversed half cycle t t of voltage of the power supply source, the time interval during which transistor PUJ, is cut off, or the phase angle of conduction of triac Tr, is smaller than in the preceeding half cycle, because a certain quantity of charge was already stored on condenser C during the preceeding half cycle t t,,,, so that at time r, a current starts to flow again through lamp LT, of slide projector 2. Likewise, in the half cycle t 1 the phase angle of conduction of the triac Tr, is further decreased to time t, at which a current begins to flow. In this way, the intensity of current flowing through lamp LT, increases and finally reaches the maximum. Variation of projection illuminance is illustrated at curve P in FIG. 3.

As far as the mode of progressively applying electric energy to the lamp circuit of only one slide projector is concerned, the process so far described is not distinct from that in a conventional projection overlapping ap paratus.

The operation of the lamp circuit of the other slide projector that has been projected will be described with respect to how the intensity of current begins to decrease in response to a connection shifting signal. Upon advent of a connection shifting signal from the remote control switch, the transfer switch element SW, cooperating with transfer switch element SW, is operated from the position, a, to the other position, b. The charge stored on condenser C, starts to leak away through resistor R and variable resistor R, to earth. However, the voltage of charge stored on condenser C, is higher than that necessary for the lamp to provide for a sufficient projection illumination, so that the triac Tr, is made conducting at a small angle of conduction. The process of conduction-of said triac is the same as that described above. The current flowing through lamp LT, during the half cycle t t is illustrated in FIG. 2B.

In a period of time t the condenser C, is charged at a voltage V, given by the formula wherein Vs is the sum of the Zener voltage of Zener diode ZD and the voltage drop of the diode D whereby the conducting of transistor PUJ is delayed by a time interval 1 1 from time I02. Therefore, the intensity of current flowing through lamp LT is slightly reduced as incidated in FIG. 28. At time r the voltage V across the condenser C is given by the formula so that the time interval during which transistor PUJ is conducting is furthermore shorted to decrease the intensity of current flowing through lamp LT as indicated in FIG. 2B. The cumulative cycle will continue until the voltage of condenser reaches a cut off voltage of transistors Tr, and Tr,, resulting in non-conductive state of transistor PUJ as well as triac Tr which causes no current to flow through lamp LT,, thereupon the lamp is completely lighted off.

As shown at curve in FIG. 3, the time at which the projection illuminance starts to decrease is shifted from t to t, by charging condenser C; at a voltage higher than that necessary for the lamp to provide for a sufficient projection illuminance. The starting of illuminance decrease is delayed by a longer time interval with a larger difference between the Zener voltages VZD and VZD, of the Zener diodes ZD, and 2D,. in a modified form of the present invention, combinations of a timer and condensers may be utilized to control the delay of opening of the lamp circuit of one slide projector with respect to the closing of the lamp circuit of the other slide projector.

The circuit of the projection overlapping apparatus of the present invention may be associated with slide changing circuits which are illustrated in FIG. 1 as including transistors Tr Tr Tr and Tr and a slide changing plunger solenoid SOL, With the circuit, the slide changing plunger is attracted or released in synchronism with a slide changing signal. The operation of the circuit is as follows. In order to replace the projected slide with a fresh one, the remote control switch SW, is closed, thereby the relay RL, is deenergized to operate the transfer switch means SW SW to the position, b. When the transfer switch element SW is set to the position, b, a trigger voltage from rectifier REC, through a diode D is applied to the base electrode of transistor Tr at which transistor Tr is made conducting. This decreases the base potential of transistor Tr to cut off it, with the result that transistor Tr, is forward biased into conduction. When the transistor Tr is forwared biased into conduction, it lowers the base voltage of transistor Tr Thus transistor Tr ceases conducting, and the solenoid SOL is deenergized.

Whilst the slide change plunger (SOL of one slide projector 2 is released, the slide change plunger (SOL,) of the other slide projector l is attracted in such a way that when the transfer switch SW is set to the position, b, condenser C, begins to be discharged and voltage across the condenser C, decreases during a time interval to the cut off level for transistor Tr This causes transistor Tr to conduct so that transistor Tr is cut off. Thus transistor Tr begins conducting and the solenoid SOL, is energized. After elapse of a certain time interval, however, the voltage across the condenser connected between transistors Tr and Tr is in- 6 creased by charging to the trigger level for transistor Tr Thus transistor Tr, is cut off and the solenoid SOL is deenergized again.

lt will be seen from the foregoing description that the described embodiment of the invention accomplishes the above-mentioned objects by providing a projection overlapping apparatus enabling sudden change of illuminance to be avoided in the projections of two successive views when the connection is shifted from one slide projection to the other slide projector, and, when so requircd, making it possible to obtain a fading effect by projecting gradually the two successive views one over the other. Therefore, a number of slides which when projected display a continuous movement of the photographed subject such as pitching in baseball mound may be projected by using two or more slide projectors in succession without wearying attention of viewers.

What is claimed is: 1. A slide projection overlapping apparatus comprising:

a plurality of slide projecting means; power supply means for providing currents to said slide projecting means for the generation of luminous energy outputs from said projecting means; switching means coupled to said supply means for opening or closing said supply means; means for generating a pulse signal for shifting the connections between said projecting means; switch control means for selectively controlling the operation of said switching means in response to pulse signal generating means; voltage control means coupled to said supply means for varying the levels of illumination of said projecting means, said voltage control means being responsive to the application of a voltage thereto from a power supply source to cause the voltages controlled by said voltage control means to linearly increase until predetermined voltage levels are reached, said voltage control means also being responsive to the cut-off voltage from a power supply source to cause the voltages controlled by said voltage control means to linearly decrease until predetermined voltage levels are reached, said voltage control means also including time delay means for delaying the commencement of decrease of voltage levels when said supply source voltage is cut off;

and wherein said power supply means is an AC voltage source provided with rectifier means for rectifying the alternating current from said AC voltage source, and wherein said voltage control means further includes time constant circuit means comprising a capacitor and a first resistor connected through said switching means to an output terminal of said rectifier means, a second resistor arranged to be connected to said capacitor when said switching means cuts off said supply means, a second switching means coupled to said supply means for controlling the supply of alternating current from said AC voltage source and a trigger means for generating a pulse for triggering the trigger circuit of said second switching means in accordance with the output of said capacitor, thereby the phase angle of conduction of said second switching means is controlled in accordance with the output of the time constant circuit so that the voltage output of said voltage control means will linearly increase or decrease.

7 2. A slide projection overlapping apparatus as described in claim 1, wherein said second switching means is a triac.

3. A slide projection overlapping apparatus as described in claim I, wherein said trigger means is provided with a third switching means which is triggered by the output of said capacitor, and

a pulse transformer connected between the trigger circuits of said second and third switching means for generating a trigger pulse by the output of said third switching means.

4. A slide projection overlapping apparatus as described in claim 3, wherein said third switching means is a programmable uni-junction transistor.

5. An apparatus for projecting images from a pair of slide projectors onto a common screen area. comprising;

an electric power source for supplying current to lamps of each of said slide projectors;

a first pair of switching means for connecting and disconnecting said electric power source to a corresponding projector lamp;

a DC. power source;

a pair of time constant circuits having a resistor and a capacitor;

means for producing a projector change over signal;

a change over mechanism which connects one of said pair of time constant circuits to said DC. power source and disconnects the other circuit from said DC. power source in correspondence with said change over signal;

a discharge path having resistor means, which is connected in parallel to the capacitor of the other time constant circuit by said change over mechanism;

a pair of trigger pulse generating means connected to each of said time constant circuits to produce a signal passing through said pair of switching means corresponding to said time constant circuits;

a voltage source for adding a voltage to the capacitor of one of said time constant circuits for delaying the start of the dimming of the projector lamp a predetermined time corresponding to said circuit when said change over mechanism disconnects one of the pair of time constant circuits from said DC.

power source;

whereby one of the projector lamps commences illumination in association with said change over signal and the other lamp illumination decrease after a predetermined time. 

1. A slide projection overlapping apparatus comprising: a plurality of slide projecting means; power supply means for providing currents to said slide projecting means for the generation of luminous energy outputs from said projecting means; switching means coupled to said supply means for opening or closing said supply means; means for generating a pulse signal for shifting the connections between said projecting means; switch control means for selectively controlling the operation of said switching means in response to pulse signal generating means; voltage control means coupled to said supply means for varying the levels of illumination of said projecting means, said voltage control means being responsive to the application of a voltage thereto from a power supply source to cause the voltages controlled by said voltage control means to linearly increase until predetermined voltage levels are reached, said voltage control means also being responsive to the cut-off voltage from a power supply source to cause the voltages controlled by said voltage control means to linearly decrease until predetermined voltage levels are reached, said voltage control means also including time delay means for delaying the commencement of decrease of voltage levels when said supply source voltage is cut off; and wherein said power supply means is an AC voltage source provided with rectifier means for rectifying the alternating current from said AC voltage source, and wherein said voltage control means further includes time constant circuit means comprising a capacitor and a first resistor connected through said switching means to an output terminal of said rectifier means, a second resistor arranged to be connected to said capacitor when said switching means cuts off said supply means, a second switching means coupled to said supply means for controlling the supply of alternating current from said AC voltage source and a trigger means for generating a pulse for triggering the trigger circuit of said second switching means in accordance with the output of said capacitor, thereby the phase angle of conduction of said second switching means is controlled in accordance with the output of the time constant circuit so that the voltage output of said voltage control means will linearly increase or decrease.
 2. A slide projection overlapping apparatus as described in claim 1, wherein said second switching means is a triac.
 3. A slide projection overlapping apparatus as described in claim 1, wherein said trigger means is provided with a third switching means which is triggered by the output of said capacitor, and a pulse transformer connected between the trigger circuits of said second and third switching means for generating a trigger pulse by the output of said third switching means.
 4. A slide projection overlapping apparatus as described in claim 3, wherein said third switching means is a programmable uni-junction transistor.
 5. An apparatus for projecting images from a pair of slide projectors onto a common screen area, comprising; an electric power source for supplying current to lamps of each of said slide projectors; a first pair of switching means for connecting and disconnecting said electric power source to a corresponding projector lamp; a D.C. power source; a pair of time constant circuits having a resistor and a capacitor; means for producing a projector change over signal; a change over mechanism which connects one of said pair of time constant circuits to said D.C. power source and disconnects the other circuit from said D.C. power source in correspondence with said change over signal; a discharge path having resistor means, which is connected in parallel to the capacitor of the other time constant circuit by said change over mechanism; a pair of trigger pulse generating means connected to each of said time constant circuits to produce a signal passing through said pair of switching means corresponding to said time constant circuits; a voltage source for adding a voltage to the capacitor of one of said time constant circuits for delaying the start of the dimming of the projector lamp a predetermined time corresponding to said circuit when said change over mechanism disconnects one of the pair of time constant circuits from said D.C. power source; whereby one of the projector lamps commences illumination in association with said change over signal and the other lamp illumination decrease after a predetermined time. 